PB1992: PROTEOMIC ANALYSIS REVEALS AUTOPHAGY INHIBITION IN MYELODYSPLASTIC SYNDROMES
Authors: Georgia Tsekoura, Andreas Agathangelidis, Xristina-Nefeli Kontandreopoulou, Aggeliki Taliouraki, Panagiotis Diamantopoulos, Nora Viniou, Vassiliki Aleporou, Issidora Papassideri, Panagoula Kollia
Journal: HemaSphere (2023)

Topic: 9. Myelodysplastic syndromes - Biology & Translational Research Background: Autophagy is an active process of intracellular enzymatic degradation of intracytoplasmic components (proteins, organelles). To date, autophagy has not been fully characterized in Myelodysplastic Syndromes (MDS). MDS represent one of the most common types of hematological malignancies in people over 60 years, being characterized by abnormalities in the maturation and differentiation of hematopoietic cells. Our initial studies at molecular level demonstrated that the expression levels of a series of genes from all stages of the autophagy mechanism were lower in MDS patients compared to healthy donors. In particular, the expression of PI3KC3, AMBRA1, UVRAG, ATG12, ATG5, ATG16, LC3B and DRAM1 genes was significantly lower in MDS patients, while the TGM2 gene showed a significant increase. Aims: The aim of our study is to confirm the loss of activity of the autophagy mechanism in patients with MDS, by determining the expression levels of the aforementioned genes at the protein level. Methods: The study group included 20 patients with MDS: 12 low-risk and 8 high-risk patients, as well as 14 healthy controls. Patients were selected on the basis of presenting with MDS symptoms without undergoing treatment. This classification was based on the International Prognostic Scoring System Revised (IPSS-R). MDS cases with IPSS-R score ≤4.5 were classified into the low-risk category, while patients with an IPSS-R score >4.5 were grouped into the high-risk category. Analysis of protein expression levels was performed by Western blotting. The intensity of the bands was quantified with ImageJ software and the expression ratio of each protein of interest relative to the GAPDH reference protein was calculated. Statistical testing was based on Student’s t-test with the difference being significant when p<0.05. Results: Our results revealed statistically decreased expression levels of LC3B, DRAM1, ATG5, ATG16 proteins while TGM2 protein levels was statistically significantly higher (p<0.05) in MDS patients compared to healthy donors (Figure 1A). The protein expression of PI3KC3, AMBRA1, UVRAG and ATG12 genes was not statistical significant lower in MDS patients. Regarding the prognosis of the disease, the protein expression was increased in the low- risk category compared to the high- risk category with LC3B, DRAM1, UVRAG proteins showing a statistically significant difference between the 2 categories (Figure 1B). In addition, high- risk patients showed a higher degree of TGM2 protein expression compared to low- risk patients (Figure 1B). Summary/Conclusion: Overall, these observations are consistent with the data of transcription analysis, indicating the reduction of the autophagy activity in MDS patients compared to healthy donors. The subsequent comparison between patients with MDS of different prognosis showed that the loss of autophagy activity was more pronounced in low risk patients, highlighting the existence of molecular differences between MDS categories. Figure 1. Expression levels of autophagy machinery proteins between: (A) MDS patients and healthy donors, and (B) Low- risk MDS patients and high- risk MDS patients. Statistically significant differences are depicted with an asterisk.Keywords: MDS